Liquid treatment



J. J. FELSECKER LIQUID 'IIREATMENT Original Filed July 6, 1942 July 23,1946.-

IN VEN TOR.

Patented July 23, 1946 FFICEL]? LIQUID TREATMENT .l

John J. Felsecker, Calumet City, Ill.,.ass'igrior to Graver Tank & Mfg.00., Inc., a corporation of Delaware Original application July 6, 1942,Serial No. 449,968, now Patent No. 2,377,545, dated June 5, 1945.Divided and this application January 10, 1944, Serial No.'517,741

1 This invention relates to liquid treatment and particularly to theremoval of suspended, colloidal, or dissolved solids from liquids bychemical and physical treatment, with clarification by sludge filtrationand sedimentation; The softening of water by an improved lime-sodaprocess is typical for many applications of the invention, and specialreference will be had to this application, which illustrates theinvention but is not intended to limit the same.

It is an object of this invention to provide an improved method andapparatus capable of purifying a liquid of solids contained and formedtherein.

' Another object is to cause a mixture of liquid and solids to flow as adistributing flow through a liquid body, spaced above the bottom andbelow the to of the liquid body, tocontrol or adjust the agitativeefiect of the solids distributing flow on solids present above and belowthe same, so as to suspend small and medium particles above the same andto settle large particles below the same, and to clarify the liquid bysludge filtration in a flow upwardly branching off from the distributingflow, and by sedimentation of solids below the distributing flow.

According to a particular feature I recirculate parts of saiddistributing flow into the mixture to be introduced, whereby changes inthe flow rate of the mixture may be compensated for, the distribution ofliquid and solids in the solids blanket may be improved, precipitationand flocculation vantages obtained.

Other objects are to provide favorable conditions for the sludge blanketand Other operative zones and parts of the liquid, as well as suitablemeans for controlling, guiding, stilling, or segreparatus embodying thisinvention.

promoted by sludge recirculation, and other ad- 440 5Claims. (01.2109162 Figure 2 is a similar view of a modified embodiment. Figure 3 is adiagram of liquidflowsinthe apparatus of Figure l. r v

The tank ID has an inlet ll, throughwhich it receives the newlyintroduced hard water,previouslyldosed with anyrequired-softeningrandscoagulating chemicals, or other 'pr'ecipitants.The tank is'shown round,'and substantiallysubdivided into threeconcentric compartments; by two annular, concentric partitions, theinner one; of which isshown at l2 and forms a central standpipe, whilethe outeris shown at l3 andiis' relatively close to the tankwall l4.These-partitions I2 and l3extend vertically from the t'opaof the tank topoints above the tank bottom I 5. An airlift or central mixing chamber16 is surrounded by the central standpipe '12, and an"annula'r chamber11 for primary precipitation treatment is confined by the tank wall l4and theinner wall l3; Radial pipes 18 are installed adjacent the top ofthe tank, between the top 'of the central standpipe l2 and the top ofthe wa1l'fl3, whereby the top of the airlift chamber l6 communicateswith the top of the'pri'mar'y precipitation chamber I'll and discharges,tangentially thereof, to provide or 'promote a spiral flow, including arotation of the liquid in said'chamber. The inlet pipe I l enters thetop of the primary chamber I1. 011 the inside of the ihnerannular walll3, and adjacent to its top, there is an annular overflow weir l9providing for the discharge of softened and clarified water into a"circular launder 20 discharging throughaneflluentconduit 2|. The weirdeterminesthe low'estpoint to which the liquid level inthe tank canfallin operation, except when the tank is drained for cleanout orrepair.4

The water received through the inlet :Il m'ay carry flocculent material,and fio'cs will be 'precipitated as the'jwater flows through the tank.The process carried out in this tank is of'the type wherein smallandmedium size flocs arecarried along or suspended by theliquidflow, whilelarge solids or flocs settle to' the tank bottom I5. This settling offlocs may start inthe primary wel1 l3, and flocs may settle on thebottom below that well; This bottom is substantially flat, especially inlarge tanks. Portions of the settled solids are continuously picked up"and laterally removed by scrapers 22, which slowly rotate over thebottom,being driven by a motor 23 and speed reducer 24,' through acentral vertical shaft 25.

The solids removed by the scrapers -arereceived in a central sump ZBfromwhich they are ulti- 3 mately Withdrawn, in well-known manner, through aconduit 21.

The'water carrying all the fiocs except the largest, which have settledout in the primary well l2 ,flOWS horizontally inwa-rd into' andthroughthe distribution zone 28, passing first below the lower edge 29of the annular wall I3 and finally upward, through the sludgefiltration, f zone 30., The distribution zone 28 is locate-din the spaceinside of the wall I3 at an elevation adjacent to that of the lower zedelifliofisaid W l, while the sludge filtrationczone :39 extends11pwardly from this distribution zone, inside of the wall l3. Therotation of the liquidacontinuesin the distribution zone 28.ltisanaidto-floccula-7,;

V straightlined and vertical.

.-:However.,:only .part of the water entering the distribution zone 28hows "upward through the sludge:filtration zone '39 and over the weirl9.

tflnotheripartl of :this water isidrawn into aibottcm openingsorropenings a 32 of the: standpipe :12, :upon

-operation 'of an airlift .=device 13:3. This :airliit device comprises:a source of compressed air (not shown), ia lpipe 2341mm that .source..to-ia slower,

inner ipart of :the :space defined my the inner periphery ZQfJifihGstandpipe 12, and :airdistributor :meansfi ab'thelend ofithis pipewithin said space.

*AS) air escapes ,from :this distributor :;a mixture of :air,".water,'sludge .and chemicals :is formed *twithin the standpipe,:andt'his mixture tendsx'to ;rise,;due to ithe Iact'athat it :has a,llowergspecific weightgfthan'ithe surrounding fluids. :Sin'ce th'e top.011 :thestandpipe fl 2 communicates with other zonesrthrough thepassage ways 1.8., l1, and ,28,

wlhichureturnito the openings 32, a:c los'e.drcirc ula tion of saidmixture'is established and :maintained, alongL-said :passage sways, and:in the .di-

traction :asiindicated. This circulation can :oon-

time in case oiaa :SIOWfidOWD or shut-down of :the throughput-flowEWhiChiDIiSBS through the sludge "filtration [zone 30am :the :overflow;weir 1| 9.

V lAsludge-fij-ltenu blanket isibuilt u-p i-n the zone (30,: Thetreatment :of the -Water is com- ;pletedrin thissludgefil-ter. Treated-wate-r;emerges ifmm :-the sludgeqfiltercand overflows over; the weir1:9,. iThesolids or yflocs -,agglomerat e, and architimately removed -bysettling down through 4 7 chemical composition may be exceedingly smallor light when originally formed. At every point of a liquid flowcontaining such precipitates in 7 process of formation, treatment, orremoval, :therewillbe found some such precipitates which "are relativelylarge, heavy, prematurely formed,

and. readily settleable, and others of intermediate size, weight, andsettling characteristics, There may he still others which are so light,smaller incomplete as to settle relatively slowly or not ito settle ;at:all. :In connection with the latter 'i ioun the jermay be mentionedthose hardness constituents which are still present in. a dissolved orsimilar state, .which have not completed their ichemicalreaction ,Withthe softening, precipitatilirlghorscoagulating reagents, or which havenot completed the :physical reaction of precipitation ;For azcomplet eunderstand-ingot the operation H *OfiiIlIlY improved process and-apparatus, it must .be ,-considered that, :when softening reagents are.added' to ga hard :water, the :resulting solid precipitates --or211.095 of hardness constituents are 'formed at differentmates,velocities, and degrees ofacompleteness. Some calcium carbonate flops of{fair :size may appear after :a few minutes, whereas zotherrsol-idparticles Offthe-same sub- ,stance'lmayrappear;only;:aftermany hours.:Also, :some of :said :flocs, :as loriginally formed 1may ib'e large orheavy, whereas other solids of the same or flocculation incident towhich they appear for the first time as suspended, solid particles orflocs.

.:In accordance herewith the water and the :rel- "and/Ely incompleteprecipitates. are continuously contacted -:vvith :a retainedsludge ofpreviously -;fcrmed precipitates of intermediate size and weight; thelargest, heaviest, completed precipitates being removed'bysedimentation, as soon as they have -:been formed. Inithis process,1iquid particle :may pass throughthe 'tank ,iin an averrage period "of:one hour ;:or 'less.

part of this period, flocs'may :becriginallyiformed, by primaryprecipitation {in the liquid particle. During the greatest partw-fthis:time the liquiid "particle, carrying a continuously decreasing amountof solids, perc'olates through the :sludge -,blanket:; that is, througha retained :mass. of solids previouslyformedangd being-newlyformeld, aglomerated, and increased :in "size. :A small solid particle-originallyformed in the primary flow may'be present :inrthis mass :for manyhours,or :even days, during which time-it generally increases in size-duetoagglomeration with :cthe-r particles previously -formed or being snewlyformed. The larger a particle becomes, the, more it tends to subsideinthe -mass or blanket of partioles. Occasionally, particles will bepartly broken up, when engaged by rapid port-ions of the spirallyrotating flow; whereupon they may .tendrto'riseagain, The spirallyrotating flow -of this invention, as stated before, is upwardly spacedand functionally separated from the quiescent sedimentation zone, .andthus disturb- 58,1105 of the sedimentation zone is prevented. Theparticles are ultimately agglomerated into large, heavy, and wellcoagulated fiocs, which'are no longer readilysubject eitherto'distintegration or togrowth under the conditions of the process. Thesearesno longerretainedin the sludge blanket,--:but removed bysedimentation. As theyset- 'tle through :the sludgeblanket and into thesubljacent-sediment zone they :displace liquid-upwardly. These downwardand upwardyexchanges ,or movements sarepreferablyallowed to (occurthroughout the whole area of thesludge (blanket, .or atleastinsubstantial parts thereoflrso as to facilitate and accelerate thegravitational separation of,-the large, heavy, and completes-docs fromthe sludge retained in thefilter'or blanket. In order to -:start theoperation I fillthextank 1-0 with-water I to the .level of (the overflowweir I 9.

Thereafter, I continuously add water and chemicals through the inlet Hand withdraw equal amounts of water through'the eliluent piped I. In

the beginning, the chemical treatment results in conditions which arenone better than those .ob-

tained in earliersoitening apparatus; and for this reason, the initialrate of flow or throughput through the tank is preferably kept veryslow, that is, ordinarily less than one gallon per square footof tankarea per minute. Withhigher ini-" tial flow rates, most of :the'flocsformed are entrained and carried out with'the water over-flowing overthe weir l9, and aisludge bed is formed only after a longer period ofinitial treatment. The desirable; slow, initial rate of flow-maybeenforced by proper' adjustment of a float-inlet .valve 38, which mayhave a disc 39actuated bya suitable ways. Even with such a slow 'rateofini.

tial flow, many of the flocs initially'formed are and remain so smallthat they are carried out overthe'weir I9. For this reason ithewaterdischarged during initial operation is 'generally'unsatisfactory forsuch use or consumptionas may be contemplated for the water when fullytreated in accordance with this invention.

Flocs of calcium carbonate and the like will settle from theslow,initial flow, to thetank bottom l5. flocsare not removed through thesludge sump 26 and the p'ipe'21. The scrapers 22 maybe kept at rest, orI may rotate them from timeto'ti'me, at a very slow'rate 'and fors'hortperiods' only.

Gradually, the whole of the sediment zone 3 'I may be filled withsettled sludge.

As the operation continues the sludge sediment tends to be built upabove the bottom zone31, into the distribution zone 28. From this momenton, if not before, the rateof flow is increased, by

proper re-adjustments of valve38 or of any other control means, so thatthe sludge present in the distribution zone 28 islargelyre-sus'pended'and the newly entering sludge is largely heldin suspension, and parts thereof are carried into the superimposed Zone 30,starting the formation of a suspended sludge blanket. Of course thechemical dosage is increased proportionally. Caution must be applied toavoid any excessive or abrupt readjustment of valves leading to a suddenor excessive increase in the rate of flow, which would cause thesuspended flocs to be entrained and carried out over the weir i9. Itmust be understood that at this point, the initial treatmentis not fullycompleted yet. The bulk of theinitial sludge filter consists of smallflocs. and this initial filter cannot be expected to provide completetreatment at a high flow rate. The flow rate may be raised gradually,and it must be anticipated that for a short time after each increase theoverflow will contain relatively more small fiocs again. Gradually,however, the overflow will become clear, and thereafter it will remainclear, even upon a further increase of the flow rate within certainlimits of tank capacity. This is due to the fact that the beneficialefiects of the sludge blanket 36 play their part increasingly; and thedocs in the sludge blanket itself become larger and heavier. A furtherincrease in the rate of throughput, as mentioned, becomes feasible; infact, it is desirable, in order to keep a sufiicient supply of flocs insuspension, and to prevent de-- pletion of the sludge blanket 36.Pursuant to this final increase of the throughput rate, the operationmay be considered normal, and may be continued indefinitely. From thisPreferably during initial operation, these.

iii)

moment on, sludge must be withdrawn through the pipe 2! at substantiallythe same rate at which new sludge is deposited; l

The sludge blanket 36 in the filtration zone according to the'presentinvention contains only, or at least primarily, the sludge which failsto settle into the sediment zone 31; that is, the does) of small andmedium size, which are readily subject to growth and agglomeration underthe conditions of the process. The flow condition affecting andsurrounding this improved slud age bed 35 in. norrrial operation; arediagrammaticallyshown in' -Figure'3. The fiowA which passes into andthrough the primary precipitation zone I! enters the distribution zone28, wherein it is continued by a horizontal, preferably spiral flow B,bringing liquid and solidsto 'all points below and inthe sludge blanket.The sludge blanket 36 as a whole is more or less stationary in thesuper-posed sludge filter zone 30, although considerableliquidmovemerits may be allowed and evenenforced therein. At all pointsof thedistributing' fiow B upward flows C are branched oil? therefrom,which enter the superposed sludge filter 36 for final treatment therein.A l A Theliquid in the spiral flow B passing through the distributingzone 28 contains precipitated flocs as well as particles'just beingprecipitated, and perhaps dissolved particles the precipitation ofwhich'has hardly started. The upward flows C carry the said particlesinto the sludge filter 36, which as mentioned consists of generallysimilar particles, of small and mediumsize. The liquid peroolatesthrough this sludge filter. Incident to this percolating flow; bothprecipitation and fiocculati'on are promoted and completed.

The largest precipitated and fiocculatedparticles contained in the flowB are constantly settled out; as shown at D. Furthermore, the largestprecipitated and flocculatedparticlesformed in the sludge filter zone 30are constantly settled out as shown at E. Otherflocs andparticlestending to turn into flocs. are continuouslyresupplied to thesludge filter, by the flow A from the primary precipitation zone l'l.They areuniformly distributed by the flow B, without undue disturbanc ofthe quiescent zone 31. Practically all the impurities contained in theliquid entering the sludge filter 36 are effectively removed from theliquid, in the sludge filter, including even the. smallest particles andthe solids most diflicult to precipitate in settleable form. Such smallparticles and incomplete precipitates are agglomerated with and thusretained by the medium and small sized, suspended flocs forming thesludge filter 36. As a result, there is a continuous growth of thesuspended flocs forming the sludge filter 36. The smallest and leastcomplete flocs. originally entrained and introduced into the filter,disappearduring this upward flow, and a well softened, clarified andstabilized water, causing no after-precipitation on continueddetentionor flow, emerges at F, to be withdrawn at G,

Flocs which have reached a large size, are no longer suspended, and ofcourse not entrained, by the upward flow C; they settle down to th tankbottom. No attempt is made to hold them in suspension. They settlethrough the distribution zon 28, where they may be engaged, partlybroken up and resuspended by the spiral flow for a while; but theyultimately settle further into the sediment zone 31 and are removed bythe scrapers 22, at H. i Whenreference is had to flocs of certain sizes,of course it will be understood that generally speaking, the largestflocs are also the heaviest ones, and settle more rapidly, or overcomean upsmalleraand; lighter ,flocs. Other features than size andspecific-weight may afiect the settleabilbottom:-First, thesediment-zone or bottom zone 31;: second,th'e distribution or spiralflow zone 28 third, the sludge filter or'sludge blanket zone 30;

and; fourth, the zone of. treated and clarified water adjacent to thelaunder 2.0. The primary zone Il may beviewed as part of the spiral flowzone 28.

into one another unobstructedly, except-as stated. Necessary'steps ofthe precipitating and coagulatingtreatment occur ineach of the zones,except the sediment zone 3! and the clear Water zone. It may be saidthat precipitation andv coagulation starts inthe primary zone H,continues in the distribution zone'28, and is. completed in the sludgevice 35 and returned to the distribution zone 28. r

In order to speed up the starting operation, it is desirable that theopenings 32 be located as close as'possible to thesludge whichaccumulates gradually on the bottom of the tank. Thus the openings 32should be relatively close to the tank bottom, at; the start. However,when a suspended sludge bed 36 has been built up and substantiallystabilized to the proper condition for normal operation, it ispreferable that the openings 32 be spaced relatively farther above thetank bottom. The reason for this is that, as mentioned, light andmedium-weighted sludge particles are most desirable in the sludge bed36; such particles therefore should be recirculated by the airlift; butthe heaviest particles, rather than these more desirable ones are foundnear the tank bottom.

During a generally normal operation, the condition of the sludge bed 35is subject to changes, upon any slow-down or speed-up of throughput andchemical feed, change of solids concentration, type of solids,pH,-temperature, and other conditions of the incoming water, changes inthe schedule of sludge withdrawals through the pipe 21, and otherchanges. Asa result, the sludge bed will tend toehang as to overalldepth thereof, as to percentage of total solids. and of mediumsizedsolids, as to Specific weight of medium-sized solids, and in otherrespects. Such resulting changes, again, may frequently call for are-adjustment of the location of the openings 32. For instance, if thebed is starved of solids of sufilcient size and weight, it will bedesirable, at least temporarily, to lower. these openings.

. 8 liquid circulatiomcaused by. thegair lift; is rapid. This, ofcourse; willnecessitate the removal of a relativelydiluted sludge, solong'as the pipe 21 is usedafonthist purpose; and such" operation willbe3,112; exception rather than the: rule, in most tanks constructed-inaccordancezzherewith. I Such a. change, in ..the:.locationfof theopenings 332::may also allect the speed ofrrecirculation; sinceaiheavier sludge will berecirculated at a slower raterthanl alightlsludge; however, this secondary efiectzgenerallyis...insignificant, in the water treatments contemplated herein; .On theother It will be understood that the saidzones' merge 1 hand, thespeed.or recirculatiommaybe changed arbitrarily;.- by adjustment? of;throttlevalve 44- in the r air? inlet'pipe 34. suchra ire-adjustment; of

velocity of? re circulation may either promote or counter 'a'ct theeffects ef: 2. Ireadjustment in the location.- of the; openings 3-2:;however, these two methods; of re adjustment iare not equivalent tooneea-nother; li'orinstance; atthe-start of operations; iti'sjdisti-nctly" more desirableto-lower the openings 32 thanitbf enlargethe? opening through the; throttle .valve 44, although both operationswould haveorre effect in commonJ'they speed up the-return oixsludgetothe'distri'bution zone 28. The-disadvantage in resorting to. a; morerapid air feed, at. thatstage, is due to the fact that-undesirablecomminution "of flocs might resulttthe floc being particularlysensitive'and destructible duringthisearly'st'age ofoperati'onsb Variousstructures can be usedtmachieve the vertical, adjustment .of .theopenings 32: as 'ex-- plained: In. the preferred, embodiment of Figurel,t-he standpipel2 consists ofitwo pipes: 45 and 46 having telescopicengagement with one another.v Pipe 45 forms the upper andwouter part of,=the standpipe While a-pipe; tubeorringv 46 formsthe lower and.inner/part. Thislower and inner part i -closed at the bottom by a plate41-, but has:' a series of openings '32-: around the side wallthereof,adjacentthebottom plate 41. Vertical rods As aresecured to thetop of the lower, innerpipe-46 and extendi o points adjacent the top'of;the tank, whereby these rods, and the lower pipe or; ring. 46. withopenings 32' can be raised or lowered by hand, or by suitable powermeans (not shown). 1

A. modification is shown by Figure 2 which. in general. provides similarparts. and operation as Figure 1 does, butwherein inlet openings Bl ofthe; airlift tube 92 are provided in superposed rows, causing a.particularly good and-deep distribution ofthe circulating flow below orthrough the sludgefilter, whereby higher rates of circulationmay beprovided without undue; disturbance of the sludge bed. An adjustmentsimilar to that of Figure l may he -provided by slidable ring members.or gates 93. Thesering members are c0ncentric:with-the air lift tube 92;they may restrict or close-some. of the superposed openings 9 I,depending on their verticaladj-ustment,andthey may be vertically--adujstable individually on conjointly; It. willbeseen: that by means of.this. modification, boththe vertical location and the eiiective depth ofthesetof; openings ill and. of the distributing flowtB entering thesame. canbe changed. A change in. effective depth or size of. this setof opening is sometimes-desirable, since the size initially selected maybe -foun'dexcessive or insufficient requiring undesirablyh-igh or lowvelocities of air'feed; these velocities havingvarious effects asexplained, upon the: speed of recirculation, type of sludge entering.the; recirculatiom type of sludge discharged into the sludge bed,distribution of materials in the distribution zone andisoqon.

Variou modifications other than those specifically shown and describedwill suggest themselves to persons skilled in the art, upon a study andconsideration of this disclosure. It will be understood that thedimensions, flow velocities, and similar data specified herein arestated only for illustration, and are not intended to limit thisinvention.

This is a divisionn of my application, Serial No. 449,968, filed July 6,1942, which has now matured into Patent No. 2,37 7,545.

I claim:

1. Apparatus for liquid treatment comprising a tank having a peripheralwall, an annular baflle concentric with said wall and extending from apoint adjacent to the top of said tank to a point above the bottom ofsaid tank, thereby separating an outer primary chamber from an innersludge filtration zone, inlet means adapted to discharge liquid to betreated and any reagents required into said tank remotely from said slude filtration zone, liquid outlet means adjacent to the top of said tankin the space inside said annular bafile, circulator means adapted tocause a flow from the space within the lower part of said annular baflieto the space outside of the upper part of said annular baffle, sludgeoutlet means associated with the bottom of said tank, and means adaptedto convey sludge over the bottom of said tank to said sludge outletmeans, said circulator means comprising a fixed updraft tube centrallyand vertically disposed in said tank, means for liquid communicationbetween the top of said updraft tube and the space between saidperipheral wall and said annular bafile, a movable tube in telescopicrelationship with the lower part of said fixed updraft tube, and meansto set the movable tube in a predetermined position, aid tubes beingadapted to provide liquid communication with the lower part of saidsludge filtration zone at an elevation which depends on the setting ofsaid movable tube.

2. Apparatus for liquid treatment comprising a tank, two annularpartitions concentric with said tank, extending from adjacent the top ofsaid tank to points above and adjacent to the bottom of said tank, andforming an inner mixing chamber and two outer chambers in said tank,means for liquid communication whereby the top of said mixing chambercommunicates with the top of one of said outer chambers which therebyserves as a primary precipitation chamber, the other outer chamber beinga chamber for sedimentation and sludge filtration, inlet means adaptedto discharge liquid to be treated and any reagents required into one ofsaid chambers other than said sedimentation chamber, liquid outlet meansin said sedimentation chamber adjacent the top thereof, sludge outletmeans in said tank vertically spaced below said liquid outlet means,circulator means adapted to maintain a liquid circulation through saidmixing chamber, downwardly through said primary precipitation chamberand in an inward flow back into said mixing hers which thereby serves asa primary precipitation chamber, the other outer chamber being a chamberfor sedimentation and sludge filtration, inlet means adapted todischarge liquid to be treated and any reagents required into one ofsaid chambers other than said sedimentation chamber, liquid outlet meansin said sedimentation chamber adjacent the top thereof, sludge outletmeans in said tank vertically spaced below said liquid outlet means,circulator means adapted to maintain a liquid circulation upwardlythrough said mixing chamber, downwardly through said primaryprecipitation chamber and in an inward flow back into said mixingchamber, the bottom of said mixin chamber communicating with the otherchambers through at least one opening, and means associated with theinner annular partition, adapted to raise and lower said opening.

4. Apparatus according to claim 3 comprising means associated with theinner annular partition, adapted to enlarge and restrict said openingincident to said raising and lowering thereof.

5. Apparatus for liquid treatment comprising a tank, two annularpartitions concentric with said tank, extending from positions adjacentthe top of said tank to positions above and adjacent to the bottom ofsaid tank, and forming an inner mixing chamber and two outer chambers insaid tank, the top of said mixing chamber communieating with the top ofone of said outer chambers which thereby serves as a primaryprecipitation chamber, the other outer chamber being a chamber forsedimentation and sludge filtration, inlet means adapted to dischargeliquid to be treated and any reagents required into one of said chambersother than said sedimentation chamber, liquid outlet means in saidsedimentation chamber adjacent the top thereof, sludge outlet means insaid tank vertically spaced below said liquid outlet means, circulatormeans adapted to maintain a liquid circulation upwardly through saidmixing chamber, downwardly through said primary precipitation chamberand in an inward flow back into said mixing chamber, the bottom of saidmixing chamber communicating with the other chambers through at leastone opening, gate means associated with the inner annular partitionadjacent said opening, adapted to be raised and lowered with respect tosaid opening, and means extending from said gate means upward to the topof said tank to raise and lower said gate means.

JOHN J. FELSECKER.

